Field of Invention
The subject matter of this disclosure is in the general field of uses of stabilized hydrogen peroxide. More specifically, said subject matter is in the field of methods for using stabilized hydrogen peroxide for in-situ chemical oxidation treatment of soil and/or groundwater.
Background of the Invention
Fenton's reaction is hydrogen peroxide that is catalyzed by Ferrous Iron (II) at a pH of 3.5 to 5.0 units. The Fenton's reaction is also known as catalyzed hydrogen peroxide (“CHP”). Chemically, hydrogen peroxide molecules in the solution are catalytically converted into hydroxyl radicals, water, and oxygen gas. The generated hydroxyl radicals can destroy a wide variety of organic compounds and, as a result, CHP is used for environmental remediation by in-situ chemical oxidation of soil and/or ground water contaminants (see e.g., U.S. Pat. No. 5,520,483 by Vigneri (circa 1996)).
Problems arise during use of CHP for in-situ soil and water treatment. First, production of the hydroxyl radicals by CHP produces a significant amount of oxygen gas and the reaction is extremely exothermic. In-situ temperatures over 220 degrees Fahrenheit have been measured during the catalyzation of 17.5% peroxide, while temperatures as high as 186 degrees F. have been recorded during catalyzation of 10% peroxide. Said exothermic reaction and production of oxygen gas can create health and safety issues when injected into the subsurface during in-situ soil and water treatment because subsurface pressures can rapidly build-up wherein the peroxide and contaminants may be forced upward to the ground surface (a phenomena known as chemical “daylighting”). Second, the lifespan of the hydrogen peroxide in a CHP reaction is short (typically less than twenty-four hours) so that the total amount of hydrogen peroxide may be entirely consumed prior to complete dispersion thereof into the in-situ treatment area. Without complete disbursement, a limited destruction of VOC contaminants in the in-situ area will occur. Thus, a need exists for methods of employing stabilized peroxide for in-situ soil and ground water treatment, wherein health and safety issues are controlled, the risk of chemical daylighting is reduced, and the hydrogen peroxide lifespan is increased (i.e., stabilized).
Not surprisingly, some have discovered ways to employ peroxide for in-situ soil or water treatment using various types of stabilized hydrogen peroxide. For instance: U.S. Pat. No. 6,319,328 by Watts, et al. (circa 2001) and U.S. Pat. No. 8,366,350 by Swearingen et al. disclose use of hydrogen peroxide that is stabilized by adding phosphoric acid and monopotassium phosphate to chelate the iron; U.S. Pat. No. 5,130,053 by Feasey, et al. discloses the concept of stabilizing concentrated hydrogen peroxide via incorporation of sodium or potassium salts; U.S. Pat. No. 5,741,427 by Watts, et al. discloses a method of treating contaminants in soil or ground water by using an oxidizing agent with various phosphates and iron; U.S. Pat. No. 8,178,742 by Innocenti, et al. discloses use of hydrogen peroxide for in-situ treatments of soil or ground water with iron chelates by diffusing the area for six to forty-eight hours with a chelating agent prior to introduction of the peroxide; and other known methods or processes for in-situ treatment of soil and ground water use hydrogen peroxide stabilized by chelating the Iron via Ethylenediamine tetraacetic acid (“EDTA”) or Phosphate based chelating agents.
Although, these known ways for stabilizing the hydrogen peroxide for in-situ treatment of soil or ground water may result in extended peroxide lifespans (albeit not well defined), the same rely on iron chelates and other chemicals that are not entirely safe or optimal for in-situ soil and ground water treatment. For instance, EDTA breaks down into nitrilotriacetic acid (“NTA”), which is a suspected carcinogen. Similarly, phosphate based chelating agents, including phosphonates, are considered fresh water contaminants and cause eutrophication in lakes and rivers. Other chelating agents are complex and expensive. Finally, the known methods of in-situ soil and ground water treatment using stabilized peroxide do not account for variable in-situ environments and do not include continual measurement and control of subsurface pressure and temperature whereby treatments cannot be customized. Thus, a need remains for methods of employing stabilized hydrogen peroxide for customized in-situ treatments of soil and ground water that (a) minimize the potential for health and safety concerns of chemical daylighting and (b) increase hydrogen peroxide lifespans.